A clinical trial with random assignment to limited radiotherapy fields (involved field, IF) or extended fields (EF) was begun in 1967 and completed case accession in 1973, with 460 eligible patients assigned to IF, 220, and EF, 240. A total of 78 deaths have been reported, 39IF and 39EF, and the remaining 181 IF and 201 EF surviving patients are being followed with the aims (1) of obtaining outcome data through 10 years from enrollment and (2) of obtaining outcome data through 8 years from early extension of disease. Outcome is measured in terms of survival, survival free of extension, complications of therapy, number of extensions, and therapy used in follow-up. The principal comparison is that of the IF and EF regimens, for the total enrolled populations and for sub-groups defined in terms of initial characteristics of age, sex, stage of disease, symptomatology, histologic type, use of laparotomy in staging, and use of abdominal radiotherapy fields. Secondary comparisons are made to estimate the prognostic significance of the above initial characteristics on survival and the significance of early local extension, extranodal extension, and transdiaphragmatic extension on survival.